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At least 631 records · Page 35Linked to original sources
USGS1993

Growth and mortality of larval sunfish in backwaters of the upper Mississippi River

We estimated the growth and mortality of larval sunfish Lepomis spp. in backwater habitats of the upper Mississippi River with an otolith‐based method and a length‐based method. Fish were sampled with plankton nets at one station in Navigation Pools 8 and 14 in 1989 and at two stations in Pool 8 in 1990. For both methods, growth was modeled with an exponential equation, and instantaneous mortality was estimated by regressing the natural logarithm of fish catch for each 1‐mm size‐group against the estimated age of the group, which was derived from the growth equations. At two of the stations, the otolith‐based method provided more precise estimates of sunfish growth than the length‐based method. We were able to compare length‐based and otolith‐based estimates of sunfish mortality only at the two stations where we caught the largest numbers of sunfish. Estimates of mortality were similar for both methods in Pool 14, where catches were higher, but the length‐based method gave significantly higher estimates in Pool 8, where the catches were lower. The otolith‐based method required more laboratory analysis, but provided better estimates of the growth and mortality than the length‐based method when catches were low. However, the length‐based method was more cost‐effective for estimating growth and mortality when catches were large.

upper Mississippi River↗
USGS1993

Annual movements of shortnose and Atlantic sturgeons the Merrimack River, Massachusetts

We used biotelemetry to study the movements of 23 adult shortnose sturgeons Acipenser brevirostrum and 23 subadult Atlantic sturgeons Acipenser oxyrhynchus oxyrhynchus in the lower 46 km of the Merrimack River between 1987 and 1990. Shortnose sturgeons used two freshwater reaches and one saline reach annually. Sexually mature fish began moving upriver from freshwater wintering areas to a spawning site in April, when increasing river temperature reached about 7°C and decreasing river discharge reached about 570 m 3 /s. Following spawning in late April–early May, fish moved downriver either to a freshwater reach where they remained all year or farther downriver to a saline reach where they remained for up to 6 weeks. After fish used the saline reach, they returned upriver to fresh water. Atlantic sturgeons entered the river from coastal waters by mid–late May, when increasing river temperatures reached 14.8–19.0°C and decreasing river discharge reached 303–675 m 3 /s, occupying a saline reach with 0.0–27.5‰ salinity. After using the same saline reach visited briefly in spring by shortnose sturgeons, Atlantic sturgeons emigrated from the river by October when maximum river temperatures were 13.0–18.4°C. We observed no tagged Atlantic sturgeons in the river in successive years. Except for use of the saline reach during spring, the two species were spatially separate.

Massachusetts↗
USGS1993

Influence of phosphorus rainbow trout diets on phosphorus discharges effluent water

Two experiments were conducted with rainbow trout Oncorhynchus mykiss to investigate the influence of several diets and supplemental phosphorus on discharges of phosphorus in hatchery effluent water. A diet was formulated to contain no fish meal and a reduced level of non‐phytin phosphorus (approximately 0.9%) provided, in part, by supplemental defluorinated rock phosphate, which has a low solubility in water. Feeding rainbow trout this diet supported 86% of the growth attained with a conventional hatchery diet while discharges of phosphorus in the effluents decreased by 40–51%.

Transactions of the American Fisheries Society↗
USGS1994

A microassay for gill sodium, potassium-activated ATPase in juvenile Pacific salmon

A microassay well-plate method is described for determining Na + ,K + -ATPase activities of small gill sections from juvenile Pacific salmon Oncorhynchus spp. The method differs from the established macromethod by detecting inorganic phosphate in nanomole rather than micromole concentrations. This permits the use of much smaller tissue samples, which makes it possible to release fish after sampling. Use of sonication during enzyme extraction and elimination of the need to deproteinize samples before ATPase analysis further simplify the assay. Application of the microwell-plate technique for both Na + ,K + -ATPase activity and protein analysis permits rapid processing of many samples. It also produces results equivalent to those of the macroassay; no significant differences occurred between sample duplicates run by the two methods with the same enzyme extract ( P > 0.05). The coefficient of variation (100·SD/mean) for microassay samples containing enzyme activities of at least 10 umol inorganic phosphate per milligram protein per hour was 12% or less for between-plate comparisons and 5% or less for same-plate comparisons. Monitoring of gill-clipped fish during migration indicated that small gill clips did not cause mortality or alter migration behavior of juvenile salmonids tagged with passive integrated transponders. These are important considerations in programs for monitoring species listed under the U.S. Endangered Species Act.

Transactions of the American Fisheries Society↗
USGS1994

Energy density and size of pelagic prey fishes in Lake Ontario, 1978-1990: Implications for salmonine energetics

We describe dynamics of energy density and size of Lake Ontario alewife Alosa pseudoharengus and rainbow smelt Osmerus mordax , and we use a bioenergetics model of a common pelagic piscivore, chinook salmon Oncorhynchus tshawytscha , to demonstrate the effect of these factors on piscivore daily ration during 1978–1990. The energy density of alewives varied more than twofold between peaks in September (age 1) or October–November (age ≥2) and the lows in May (age 1) or July–September (age≥2). The previously described seasonal pattern of energy density of Lake Michigan alewives was similar except that energy density of older alewives (age≥3) was markedly higher in Lake Michigan. During 1978–1990, the spring energy density of Lake Ontario alewives peaked in 1979 (6,259 J/g wet weight), declined irregularly until 1985, and then remained stable through 1990 (at approximately 4,600 J/g). The initial decline may have been a density-dependent response to a burgeoning alewife population, but the lack of an increase in alewife condition in the late 1980s, when alewife biomass fell, suggests a decline in lake productivity. Energy density of rainbow smelt increased with age in Lake Ontario and condition was invariant during 1978–1990 despite a threefold change in rainbow smelt biomass. Rainbow smelt energy density was lower and fluctuated less seasonally in Lake Ontario than in Lake Michigan. Mean weight of alewives aged 2 and older dropped from 41 g in 1978 to 19 g in 1989 in Lake Ontario. Rainbow smelt aged 2 and older showed a drop in mean weight from 13–17 g in 1978–1982 to 8 g in 1990. This downward trend in mean size of alewives was correlated with the sizes of alewives consumed by Lake Ontario chinook salmon during 1983–1987. For adult chinook salmon to maintain a constant growth rate during 1978–1990, mean individual daily ration during June–October had to increase from a low of 2.2% body weight/d (or 1.5 prey fish/d) in 1979 to 3.1% body weight/d (3.7 prey fish/d) in 1988. This increase in forage demand may have caused the observed declines in individual condition of salmonines over this period.

Transactions of the American Fisheries Society↗
USGS1994

Requirement of rainbow trout for dietary phosphorus and its relationship to the amount discharged hatchery effluents

Fingerling rainbow trout Oncorhynchus mykiss with initial mean weights of 9 g (small fish) and 35 g (large fish) were fed diets adequate in all known nutrients except phosphorus (P). In two experiments, triplicate lots of rainbow trout were fed basal diets containing either 0.14 or 0.41% non‐phytin P, with or without graded levels of supplemental P. Deficiency of P reduced growth, feed efficiency (weight gained/weight fed), bone ash, and whole‐body ash contents. The requirement for non‐phytin P by small trout for maximum growth and feed efficiency was not more than 0.41% of diet: The requirement by large trout was between 0.34 and 0.54% of diet. The requirement of non‐phytin P for maximum bone ash development was about 0.51% of diet for small trout and more than 0.54% for large trout. Whole‐body phosphorus content of small trout suggested a requirement above 0.51% but not more than 0.61% non‐phytin phosphorus. Although an effect of size of trout on the requirement was not clearly demonstrated, these results show that trout required more dietary P for bone mineralization than for weight gain. The minimum dietary requirement for non‐phytin P for bone mineralization was probably between 0.54 and 0.61% of diet. Discharges of P into effluent water increased significantly as trout were fed increasing levels of P. When trout were fed 0.61% available P, approximately 67% of P consumed was retained, and discharges of soluble P in effluents were 2.0 g P/kg weight gain or 1.8 g P/kg feed fed.

Transactions of the American Fisheries Society↗
USGS1994

Problems of stock definition in estimating relative contributions of Atlantic striped bass to the coastal fishery

Stock contribution studies of mixed‐stock fisheries rely on the application of classification algorithms to samples of unknown origin. Although the performance of these algorithms can be assessed, there are no guidelines regarding decisions about including minor stocks, pooling stocks into regional groups, or sampling discrete substocks to adequately characterize a stock. We examined these questions for striped bass Morone saxatilis of the U.S. Atlantic coast by applying linear discriminant functions to meristic and morphometric data from fish collected from spawning areas. Some of our samples were from the Hudson and Roanoke rivers and four tributaries of the Chesapeake Bay. We also collected fish of mixed‐stock origin from the Atlantic Ocean near Montauk, New York. Inclusion of the minor stock from the Roanoke River in the classification algorithm decreased the correct‐classification rate, whereas grouping of the Roanoke River and Chesapeake Bay stock into a regional (“southern”) group increased the overall resolution. The increased resolution was offset by our inability to obtain separate contribution estimates of the groups that were pooled. Although multivariate analysis of variance indicated significant differences among Chesapeake Bay substocks, increasing the number of substocks in the discriminant analysis decreased the overall correct‐classification rate, Although the inclusion of one, two, three, or four substocks in the classification algorithm did not greatly affect the overall correct‐classification rates, the specific combination of substocks significantly affected the relative contribution estimates derived from the mixed‐stock sample, Future studies of this kind must balance the costs and benefits of including minor stocks and would profit from examination of the variation in discriminant characters among all Chesapeake Bay substocks.

Maryland↗
USGS1994

Effects of multiple acute stressors on the predator avoidance ability and physiology of juvenile Chinook salmon

Northern squaw fish Ptychocheilus oregonensis are the predominant predators of juvenile Pacific salmonids Oncorhynchus spp. in the Columbia River, and their predation rates are greatest just below dams. Because juvenile salmonids are commonly subjected to multiple stressors at dams in the course of their seaward migration, high predation rates below dams may be due in part to an increase in the vulnerability of stressed fish. I conducted laboratory experiments to examine the predator avoidance ability and physiological stress responses of juvenile chinook salmon O. tshawytscha subjected to treatments (stressors) designed to simulate routine hatchery practices (multiple handlings) or dam passage (multiple agitations). Both stressors resulted in lethargic behavior in the fish, and agitation also caused disorieniation and occasional injury. When equal numbers of stressed and unstressed fish were exposed to northern squawfish for up to 1 h, significantly more stressed fish were eaten, but this effect was not evident during longer exposures. The lack of differential predation in trials lasting up to 24 h can be explained by the rapid development of schooling behavior in the prey, but other possibilities exist, such as changing ratios of stressed and unstressed prey over time. Concentrations of plasma cortisol, glucose, and lactate in fish subjected to multiple stressors were similar and sometimes cumulative, returned to prestress levels within 6-24 h, and correlated poorly with predator avoidance ability. My results suggest that juvenile salmonids are capable of avoiding predators within 1 h after being subjected to multiple acute stressors even though physiological homeostasis may be altered for up to 24 h. Therefore, because juvenile salmonids typically reside in lailrace areas for only a short time after dam passage, measures aimed at reducing physical stress or protecting them as they migrate through dam tailraces may help alleviate the relatively intense predation in these areas.

Transactions of the American Fisheries Society↗
USGS1994

Effects of salinity on striped bass eggs and larvae from the Savannah River, Georgia

Operation of a tide gate installed in the Savannah River by the U.S. Army Corps of Engineers to reduce dredging activities increased salinities upstream in important spawning habitat for striped bass Morone saxatilis . To assess the effects of salinity on survival and growth of striped bass at early life stages, newly fertilized eggs and 48‐h‐posthatch larvae were exposed to serial dilutions of seawater, with salinities ranging from 0 to 33‰ (g/L) in increments of 3‰; in addition, older larvae (5‐d posthatch) were exposed to salinities of 0, 6, 12, 18, and 24‰. Eggs were exposed until 24 h posthatch, 48‐h‐posthatch larvae were exposed for 10 d, and 5‐d‐posthatch larvae were exposed for 6 d. Eggs died within 24 h in salinities greater than 18‰. Both survival and total length of larvae hatched from eggs exposed to salinities of 15‰ or higher were reduced. Percent mortality and mean total lengths of newly hatched larvae followed the same pattern for each of three sets of salinity regimes (i.e., changes in salinities over time) that striped bass eggs might encounter during passage downstream in the Savannah River. Hardening eggs in freshwater did not increase survival or length of hatched larvae over that shown by eggs hardened in saline water. The 5‐d‐posthatch larvae were less sensitive to salinity than the 48‐h‐posthatch larvae. Survival of larvae was negatively correlated with both salinity and exposure time. For 48‐h‐posthatch larvae, the 10‐d LC50 (the salinity lethal to 50% of the test fish within 10 d) was 10‰. Probabilities of survival for larval striped bass exposed to different salinities for different amounts of time can be estimated from curves generated from models of survival analysis. Salinities judged to be critical to Savannah River striped bass eggs and larvae are those greater than 9‰.

Georgia↗
USGS1994

Tag recovery estimates of migration of striped bass from spawning areas of the Chesapeake Bay

In 1988–1991 striped bass Morone saxatilis were collected for tagging from various spawning areas within the Hudson River (New York) and the Chesapeake Bay (Maryland). The fish were tagged and released during traditional periods of spawning and recovered by commercial and recreational fishermen. The proportion of fish that migrated in spring–fall from spawning areas in Chesapeake Bay to more northern waters of mid‐Atlantic and New England states was estimated from the geographically stratified tag returns. Most of the tagged fish were 40–100 cm total length (TL). The estimated proportion of migrant striped bass increased with body size, and nearly all fish larger than 100 cm TL left the bay during the spring–fall migration. Sex‐specific differences in migration appear to be associated with the differences in body size of mature males and females, thus lending support to previously hypothesized patterns of striped bass migration.

Maryland↗
USGS1995

Evidence for lack of homing by sea lampreys

Recently metamorphosed sea lampreys Petromyzon marinus were captured in the Devil River, a tributary to Lake Huron, during summer and autumn 1990. They were tagged with a coded wire tag and returned to the river to continue their migration to Lake Huron to begin the parasitic (juvenile) phase of their life. During the spawning run in spring 1992 when the tagged animals were expected to mature and return to spawn, sea lampreys were trapped in nine tributaries to Lake Huron, including the Devil River; 47,946 animals were examined for coded wire tags, and 41 tagged animals were recovered. None of the 45 mature sea lampreys captured in the Devil River in 1992 were tagged, a proportion (0%) significantly lower than the proportion of the recently metamorphosed sea lampreys tagged in 1990. The distribution of tag recoveries among streams lakewide, however, was proportional to catch. Tagged sea lampreys did not appear to home, but instead seemed to select spawning streams through innate attraction to other sensory cues.

Transactions of the American Fisheries Society↗
USGS1995

Growth and survival of newly parasitic sea lampreys at representative winter temperatures

Larval sea lampreys Petromyzon marinus begin to metamorphose into their parasitic phase in July and migrate to the Great Lakes either in autumn, when they immediately feed on fish, or in spring after overwintering in the stream substrate. Survival and growth of newly parasitic autumn migrants (mean weight, 4.18 g) differed significantly between temperature treatments when sea lampreys were held over winter and allowed to feed on longnose suckers Catostomus catostomus at either the maximum available temperature (&tilde;4&deg;C) or normal surface temperature (minimum <1&deg;C) in the Great Lakes during winter. Survival from December 1990 to June 1991 was 60% for the animals held in the warmer water but only 30% for the animals held in the colder water until 23 April. The average increase in weight was 8.23 g for the 35 survivors in the warmer water but only 5.15 g for the 17 survivors in the colder water. Average increases in weight from December to May for sea lampreys at both temperatures were 3.8 to 6.6 times greater than increases reported previously. A newly metamorphosed sea lamprey that migrates to the Great Lakes in autumn could be 2.5 to 3 times larger in June than one that overwinters in the stream substrate, where it cannot feed, and migrates in spring. Hence, autumn migrants may have an advantage in growth and survival over spring migrants, particularly if food supply is adequate in the warmest stratum of the lake during winter.

Transactions of the American Fisheries Society↗
USGS1995

Evidence of impaired reproduction by Western mosquitofish inhabiting seleniferous agricultural drainwater

Western mosquitofish Gambusia affinis from the San Luis Drain (SLD), a major conveyance system for seleniferous agricultural subsurface (tile) drainage water in the San Joaquin Valley, California, experienced lower reproductive success than did mosquitofish from a nearby reference area (Pond 26 at the Volta Wildlife Area, VOLTA) that had no history of receiving tile drainage. At birth, mean survival of SLD fry was 70% in 1984 and 77% in 1985, whereas mean survival of VOLTA fry was greater than 99% in 1984 and 97% in 1985. Measurements of total length (TL) of offspring born to SLD females in 1985 showed that stillborn fry (mean TL, 7.5 mm) were significantly shorter than live fry (mean TL, 9.4 mm). In addition, most stillborn fry were at earlier stages of development (contained prominent yolk sacs or occasionally resembled eyed embryos) than most live fry (yolk sacs were fully resorbed). In comparison, stillborn and live fry born to VOLTA females did not differ significantly in TL (mean for stillborn fry, 7.1 mm; mean for live fry, 7.5 mm), and nearly all fry had resorbed their yolk sacs. Mosquitofish from the SLD contained over 100 μg/g (whole‐body concentration in dry weight) of selenium, whereas those from VOLTA averaged 1.5 μg/g. Although experiments are still needed to establish cause and effect, the high incidence of abnormal births of mosquitofish from the SLD is seemingly a response to selenium toxicity.

California↗
USGS1995

Ebb and flow of encroachment by nonnative rainbow trout in a small stream in the southern Appalachian Mountains

Brook trout Salvelinus fontinalis is the native salmonid species of streams in the southern Appalachian Mountains. The present distribution of this species, once widespread from headwaters to lower reaches of large streams, is restricted to mostly headwater areas. Changes in the distribution of native brook trout in the presence ofˈ nonnative rainbow trout Oncorhynchus mykiss have been documented in Great Smoky Mountains National Park. When rainbow trout were first found in a tributary (Rock Creek) in the park in 1979, a study was begun to assess changes through time in distribution and abundance of rainbow trout in Rock Creek and to compare the brook trout and rainbow trout associations in Rock Creek with associations found in other park streams. Abundance of brook trout was low in the downstream sections of Rock Creek in 1979–1993. Brook trout abundance was highest in the steep‐gradient, pool‐dominated headwater section which was only 2 km from the confluence of Rock Creek and Cosby Creek. Rainbow trout were present in low densities in Rock Creek during the same period. Although rainbow trout were most abundant in the lower stream sections and never found in the headwater section, adult and age‐0 rainbow trout were found in the middle section in 1988. Rainbow trout were absent in the middle section in 1991, but one large adult rainbow trout was present in the section in 1992 and 1993. Floods, freshets, and periods of low stream discharge appeared to play an important role in the distribution and population structure of rainbow trout in Rock Creek. The lower portion of Rock Creek was poor trout habitat because the sections were dominated by cobble–rubble substrate and shallow riffle areas. Stream habitat appeared to be better suited for brook trout than for rainbow trout in the steep‐gradient upstream sections which were dominated by boulder‐cobble substrate and deep pools. The results of this study suggest that encroachment by rainbow trout can exhibit considerable ebb and flow in steep‐gradient tributaries in the park, and they suggest substantial evolutionary adaptation by brook trout to the hydrological conditions in the Rock Creek drainage.

North Carolina, Tennessee↗
USGS1995

A non-lethal measure of smolt status of juvenile steelhead based on body morphology

A nonlethal morphometric method to assess smolt status of juvenile steelhead Oncorhynchus mykiss was validated. Fish were collected from hatcheries before release and during their seaward migration in a large river system. Fifteen anatomical landmarks were digitized from photographs of each fish, resulting in 34 morphometric characters based on a truss network. Principal component and canonical discriminant function analyses were used to assess smolt status. A single canonical variate was significantly correlated with gill Na + ,K + ‐ATPase activity, a commonly used measure of smolt status. This nonlethal method may be a useful measure of smolt status when sacrificing fish is not desirable or possible; it requires little training to perform, but it does require a larger sample size than some other methods.

Transactions of the American Fisheries Society↗
USGS1995

Developmental instability in the Pacific Hake parasitized by the Myxosporean Kudoa spp.

A morphometric study of the otoliths of a population of Pacific hake Merluccius productus was conducted to detect developmental instability (DI) related to parasitism by Myxosporeans, Kudoa spp. We report a link between parasitism and DI, which we measured as fluctuating asymmetry by comparing the right–left differences in otolith shape, width, and weight in the same fish. Otolith shape provided the most sensitive measurement of DI asymmetry. Results suggest that Kudoa spp. could be a strong agent of selection in the Pacific hake.

Transactions of the American Fisheries Society↗
USGS1996

Spawning of the shortnose sturgeon the Merrimack River, Massachusetts

We tracked 10 ultrasonically tagged shortnose sturgeons Acipenser brevirostrurn during spring in the Merrimack River to investigate spawning. Seven fish in 1989 and six fish in 1990 were tracked intensively to identify the timing and location of spawning and to characterize spawning habitat. In mid‐April 1989 and 1990, fish moved upstream to just below head of tide, concentrating in a 2‐km reach at river kilometers 30–32 (measured from the mouth) at Haverhill, Massachusetts. The estimated spawning time was a 5‐d period (26–30 April) in 1989 and an 8‐d period (22–29 April) in 1990. Spawning sites covered about 10.5 ha in 1989 and 13.5 ha in 1990. Fish spawned as river temperature increased from 9.6 to 14.0°C and river discharge decreased from 390 to 240 m 3 /s. Physical characteristics of spawning sites were boulder–rubble substrate, water depth of 1.8–5.5 m, and bottom water velocity of 0.3–0.7 m/s. We captured no ovulating females but verified successful spawning in 1990 by capturing two live embryos. Gill‐net captures and telemetry during spring showed that some males moved to the spawning area annually. The low abundance estimates of spawning fish (9 in 1989 and 16 in 1990) indicate that the shortnose sturgeon population in the Merrimack River is the smallest yet identified and is likely vulnerable to extirpation.

Massachusetts↗
USGS1996

Feeding response by northern squawfish to a hatchery release of juvenile salmonids in the Clearwater River, Idaho

We collected gut contents from northern squawfish Ptychocheilus oregonensis captured in the Clearwater River, Idaho, 0–6 km from its confluence with the Snake River, following the release of 1.1 million yearling chinook salmon Oncorhynchus tshawytscha from the Dworshak National Fish Hatchery. Before the hatchery release, northern squawfish gut contents (by weight) in the study area were 38% crayfish Pacifastacus spp., 26% insects, 19% nonsalmonid fish, and 16% wheat kernels Triticum spp. Juvenile salmonids constituted 54% of gut contents about 24 h after the hatchery release, 78% after 5 d, and 86% after 7 d. The mean number of salmonids per gut (1.2) after release was higher than typically seen in guts from northern squawfish collected in mid-reservoir areas away from hydroelectric dams on the Snake and Columbia rivers. Length-frequency distributions of juvenile salmonids eaten and those captured in a scoop trap 4 km upstream of the study area indicated that northern squawfish were selectively feeding on the smaller individuals. We attribute the high rates of predation in the study area to the artificially high density of juvenile salmonids resulting from the hatchery release and to the physical characteristics of the study area in which the river changed from free flowing to impounded. Our results suggest that northern squawfish can quickly exploit hatchery releases of juvenile salmonids away from release sites in the Columbia River basin.

Idaho↗